The present invention generally relates to improvements in the field of medical devices that use radio frequency (RF) signals. More particularly, the present invention concerns a medical device used in invasive procedures that uses RF signals for multiple applications, such as tracking an invasive instrument and improving the navigation of slender instruments during insertion and progression in the body.
Various issued patents disclose using electromagnetic waves with medical devices. For example, U.S. Pat. No. 5,377,678, issued on Jan. 3, 1995, discloses a tracking system to follow the position and orientation of a device with RF fields. In the abstract of this patent, it is stated that the system disclosed in the patent involves radio frequency signals emitted by an invasive device such as a catheter. The abstract also states that the invasive device has a transmit coil attached near its end and is driven by a low power RF source to produce a dipole electromagnetic field that can be detected by an array of receive coils distributed around a region of interest. The abstract further discloses that the position and orientation of the device, as determined by the tracking system, are superimposed upon independently acquired Medical Diagnostic images, thereby minimizing the radiographic exposure times. The content of this patent is incorporated by reference into this application as if fully set forth herein.
As another example, U.S. Pat. No. 5,445,150, and issued on Aug. 29, 1995, discloses an invasive system employing a radio frequency tracking system. In the abstract of this patent, it is stated that the system disclosed in the patent involves an invasive imaging system that employs a self-contained RF transmitter attached to an invasive device within a subject without physical connections to a tracking/display system and without the use of ionizing rays. The abstract further states that the radiated RF signal is received by receive coils of a tracking/display means, which calculates the location of the RF transmitter. The tracking/display means displays the medical diagnostic image on a monitor and superimposes a symbol on the image at a position corresponding to the calculated location of the RF transmitter. The content of this patent is incorporated by reference into this application as if fully set forth herein.
Another example is U.S. Pat. No. 6,377,839, which issued on Apr. 23, 2002, and which discloses a tool guide for a surgical tool. In the abstract of this patent, it is stated that “[a] subject is secured to a subject support (10). A stereotaxic wand (40) is inserted into a tool guide (60).” The abstract also states that the wand has two emitters which selectively emit wand signals which are received by three receivers, and that a trajectory and location of the wand are superimposed on a diagnostic image on a monitor. If the surgeon is satisfied with the entry point and trajectory shown on the monitor, a surgical tool is inserted into the bore while the tool guide is held along the designated trajectory and at the designated entry point. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A still further example is U.S. Pat. No. 6,701,176, which issued on Mar. 2, 2004, and which is entitled “magnetic-resonance-guided imaging, electrophysiology, and ablation”. In the abstract of this patent, it is stated that the system, in its preferred embodiment, provides an invasive combined electrophysiology and imaging antenna catheter, which includes an RF antenna for receiving magnetic resonance signals and diagnostic electrodes for receiving electrical potentials. The combined electrophysiology and imaging antenna catheter are used in combination with a magnetic resonance imaging scanner to guide and provide visualization during electrophysiologic diagnostic or therapeutic procedures. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A further example is U.S. Pat. No. 6,738,656, which issued on May 18, 2004, and is entitled “Automatic Registration System for use with Position Tracking an Imaging System for use in Medical Applications.” The abstract of this patent states it is a method of automatic registration which includes forming an image of a body part including a representation of markers fixed in a known position in space relative to a reference mount, positioning a sensing unit in a known position in space relative to the reference mount, and automatically registering the sensing unit in a space relative to the formed image based on the location of the markers in the formed image, the known location of the markers relative to the reference mount, and the known location of the sensing unit relative to the reference mount. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A further example is U.S. Pat. No. 6,833,814, which issued on Dec. 21, 2004, and is entitled “Intrabody Navigation System for Medical Applications.” The abstract of this invention states it is a system and method for tracking the position and orientation of a probe such as a catheter whose transverse inner dimension may be at most about two millimeters. The abstract further states that three planar antennas that at least partly overlap are used to transmit electromagnetic radiation simultaneously, with the radiation transmitted by each antenna having its own spectrum. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A further example is U.S. Pat. No. 6,251,110, which issued on Jun. 26, 2001, and is entitled “Combined Radio Frequency And Ultrasonic Surgical Device”. The abstract of this invention states that it is an energy-based surgical device for the application of ultrasonic energy and Radio Frequency energy. The abstract further states that the surgical device has a housing and an acoustic assembly having an electrically conductive waveguide, and the distal end of the waveguide of the acoustic assembly has an end effector for the conduction of ultrasonic energy or Radio Frequency energy. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A further example is U.S. Pat. No. 4,931,047, which issued on Jun. 5, 1990, and is entitled “Method And Apparatus For Providing Enhanced Tissue Fragmentation And/Or Hemostasis”. The abstract of this invention states that it is an apparatus having a vibratable tip for ultrasonically disintegrating tissue in a surgical procedure and for aspirating the disintegrated tissue and fluids away from the surgical site through an opening in the tip. The abstract further discloses that a connection to an electrosurgical unit provides for delivery of RF cutting current, RF coagulating current, or a blend thereof, to the tip so that electrosurgical procedures can be conducted separately or simultaneously with ultrasonic aspiration through the tip. The content of this patent is incorporated by reference into this application as if fully set forth herein.
There are a number of other patents that disclose tracking devices. For example, U.S. Pat. No. 7,015,859, entitled “Electromagnetic Tracking System and Method Using a Three-Coil Wireless Transmitter” and U.S. Pat. No. 6,285,902, entitled “Computer Assisted Targeting Device for Use in Orthopaedic Surgery”. U.S. Pat. No. 6,628,894 discloses a hand held camera with tomographic capability. The tomographic imaging system disclosed in the patent includes a moveable detector or detectors capable of detecting gamma radiation, one or more position sensors for determining the position and angulation of the detector(s) in relation to a gamma ray emitting source, and a computational device for integrating the position and angulation of the detector(s) with information as to the energy and distribution of gamma rays detected by the detector and deriving a three dimensional representation of the source based on the integration. The content of these patents are incorporated by reference into this application as if fully set forth herein.
Minimally invasive surgical procedures are being increasingly used to deposit or extract fluids, solid materials, or miniature devices internal to the body. Probes are being used that incorporate different devices including miniature cameras or that can apply different energy forms such as radio frequency (RF) energy to treat tissue. These types of applications require that a slender medical instrument reach a small target position internal to the body of the subject and that the position of the critical part of the medical instrument is always known through medical imaging, such as fluoroscopy.
In many cases, a user needs to insert a long flexible needle (straight or curved) through the skin and deep into soft tissues for biopsy, injection, or insertion of a smaller diameter needle or wire through the needle's cannula. The path of the needle is not necessarily straight for two main reasons. The first reason that the needle's trajectory curves is that the tip of the needle is commonly beveled to make it sharp. The user inserts the needle by pushing it along its axis and the soft tissues encountered during insertion apply a component of reaction force perpendicular to the plane of the bevel. Therefore, the tip of the needle is forced to move away from the plane of the bevel.
A second reason for the needle path varying unpredictably is that tissues of different density are encountered during insertion. The needle, in general, prefers to take the path of least resistance into the tissues that are easiest to penetrate. This path may not be the desired path.
Currently, users often use beveled curved needles to reach pathology that is unreachable by a straight path. These curved needles are usually flexible and are made of shape memory alloy (e.g., nitinol) so that they can be fed through a long, straight rigid outer shaft. They then start to bend as they exit the shaft. For example, the straight outer shaft is first inserted to a desired linear depth to one side of a critical structure with the inner shape-memory curved needle pushed out to start a curved path (tracked by fluoroscopy) around the critical structure. To steer the needle, the user changes the radius of curvature by changing the amount of needle in or out of the straight shaft and the user changes the direction of the curved path by rotating the inner curved needle within the outer straight shaft. Such a procedure requires dexterity and constant fluoroscopic imaging to ensure the proper needle path.
In addition to problems with predicting the path of the needle, it sometimes becomes difficult for the user to continue to advance the needle farther after a substantial portion of the needle is within the soft tissues. This problem occurs because the force to continue to insert the needle is the sum of the force to slice through new tissue plus the frictional resistance along the shaft of the needle that is within the tissue. As the needle is inserted farther and farther, this frictional resistance increases in direct proportion to the length of the shaft within the tissue.
Therefore, it would be desirable for the user to be able to insert a needle with better predictability of its path and with less resistance to insertion.
Radio frequency scalpels are produced by various companies (e.g., Ellman International, Oceanside, N.Y.; Meyer-Haake, Wehrheim, Germany). These scalpels have advantages over standard scalpels in that they require less force to cut tissue and the tissues do not bleed much after cutting because the small blood vessels become cauterized by the radio frequency energy. However, there exists a need for radio frequency technology to be applied to a needle tip for easier penetration with less sideways deflection to ease navigation.
A common reference for selecting the appropriate energy waveforms for certain types of procedures is described in the table on the Ellman website. The physician should be able to choose the level of energy based on whether hemostasis is desired and what types of tissues are being encountered. For example, when penetrating skin and superficial muscle, a low energy would be used, but if bone or other dense tissue were encountered, the energy could be increased.
Heretofore, the positions of surgical instruments and/or apparatuses being used during minimally invasive surgical procedures have often been tracked by taking multiple x-ray images (fluoroscopy). This method of tracking position adds time to surgical procedures, provides only discrete steps of position change, and increases the exposure to radiation energy to the subject and medical staff.
Present technology that is useful in some aspects of minimally invasive surgery is a guidance system that assists in locating the initial position of the surgical instrument and/or apparatus while it is external to the subject's body and can track rigid extensions of the instrument/apparatus that penetrate into the body. These existing guidance systems use direct line of sight and triangulation to calculate position by using two or more cameras in direct line of sight of each light source. The light sources are permanently attached to the instrument/apparatus (such as a wand) that is manually held in a spatial position relative to the subject. The position of the wand is calculated and imposed upon the diagnostic image. For tracking penetration into the subject of any kind of flexible device or of a rigid device that must penetrate deeper than the wand can allow, the position of the surgical instrument is tracked by taking multiple x-ray images. Of note, the movement of the outer surface of the subject is insufficient to account for movement of internal structures and organs. Complex internal movement can be caused by respiratory motion as well as a shift in the anatomic architecture occurring during some operative procedures (particularly partial debulking of tumor or other masses).
There are many different surgical procedures that require surgical instruments to enter the body. Many applications require that the surgery be performed using minimally invasive surgical procedures, thereby creating the minimum disturbance and damage to the tissue of the body. By using minimally invasive techniques, the risk of infection is reduced and the recovery time is shorter.
During minimally invasive surgical procedures, trying to determine the position of a surgical instrument that is internal to the body of the subject and to track the instrument's path relative to a navigation plan and to efficiently arrive at the planned target is quite cumbersome using existing technology. The efficient navigation of the surgical instrument and feedback of its precise position are critical to reducing the time and improving the quality of surgical procedures.
Therefore, there exists a need for an improvement on existing technology that tracks the precise position of a surgical device.